By the time you read this, the show may be over. But currently each night at 9pm you can turn on your telly and, in between adverts, watch someone breaking down live. It's extraordinarily entertaining to watch someone going to pieces. If you press the red button, you can even take part. You can vote to have insects rain down on her head – we know that she's frightened of insects. Or how about burying her in a coffin and having rats crawl over her face? That really will freak her out! Perhaps she'll pretend to faint again. What's she complaining about anyway? She asked for it, didn't she!

Nobody quite knows why Gillian McKeith agreed to take part in the latest series of ITV's I'm a Celebrity Get Me Out of Here! And nobody knows why she doesn't just leave. What is it that compels her to stay and take yet more punishment, instead of just walking across the bridge to five-star freedom and supportive friends (one hopes) – and, above all, to privacy, as she is perfectly free to do? The fact that she doesn't, the fact that she stays, despite the obvious cost to her mental wellbeing, does not make McKeith fair game. On the contrary, from my perspective at least, it's the most disturbing aspect of the whole business.

Reality TV is a curious phenomenon. The appeal lies not only in watching something "real" (whatever that means) but also in our detachment from it. This is intimacy with none of the complications, nothing is asked from us in return. We can watch something real without really watching, safe on the other side of the screen. We can watch somebody falling apart and know that it's all just a bit of fun. And should we start to doubt it, you can guarantee Ant 'n' Dec will pop up, like grotesque playground bullies, kidding around while their victim snivels in the corner.

I don't know McKeith. I have watched her programme You Are What You Eat, where she tries to get people to change their diet by humiliating them, essentially, or so it would appear. "You should be ashamed of yourself!" she says, standing a morbidly obese young woman in front of a table piled high with all the chocolate and cakes and ice cream and pork pies she's consumed in the previous week (this is primetime entertainment too, in case you were wondering).

Indeed, McKeith's treatment of people on her own programme appears to be regarded as justification for the treatment she herself is receiving on I'm a Celebrity. And in response she's stealing, faking fainting fits, breaking down, moaning, picking fights and crying more or less constantly. She looks dreadful too, which all adds to the fun. "Nutcase alert!" shrieks one headline above a suitably haggard, wonky-eyed picture. And now, according to some reports, she's apparently claimed to be pregnant. "At her age! Looking like that! It's priceless," is the general reaction.

But in our haste to justify our choice of victim, we are dodging the essential question: why must we victimise anyone at all? What do we get out of watching someone suffering on TV? Because with upwards of 10 million people tuning in each night, you'd have to conclude we're getting something from it.

It seems to me that McKeith has become a sort of 21st-century scapegoat, a term that derives originally from the ritual of Yom Kippur, the day of atonement. A goat was symbolically laden with the sins of the people before being sent into the wilderness to be destroyed. McKeith symbolises everything we secretly despise within ourselves. Bullying, manipulative, weak and pathetic. In "destroying" her, we seek to absolve ourselves, or at the very least to distinguish ourselves, to say: "I am not like that." But, of course, we are like that. It's we after all who put her there – we loved to watch Gillian bullying fatties. If we weren't like that, we wouldn't need to do it.

The problem is that scapegoats don't really work. We are all a mass of contradictions; callous and compassionate, courageous and pathetic. We can't simply disown the bits we don't like by sticking them on some convenient other and throwing stones. That's just not reality, is it?